1. Field of the Invention
This invention relates to a magnetic record reproducing method, and in particular, to a magnetic record reproducing method which is capable of accomplishing high-speed reading.
2. Description of the Prior Art
Heretofore, development of magnetic tapes, magnetic discs, or the like, as memories for recording image information such as animation images and still images obtained by 8 mm VTR, electronic still cameras, or the like, or as the external memories of computers, has been actively carried out. The magnetic record reproducing method of this type generally comprises using a magnetic head such as a ring head, an MR head or a vertical head to detect the direction or density of signal magnetization on a medium and electrically reproducing information.
On the other hand, there has been proposed a magnetic transfer film reproducing method using a magnetic garnet film or the like as a magnetic transfer film to optically reproduce information. The magnetic transfer film reproducing method comprises bringing a magnetic transfer film into intimate contact with a magnetic recording medium, transferring the signal magnetized section of the recording medium to the transfer film by a leakage magnetic field, applying a laser light to the transfer film, and reproducing the transfer film by utilizing the rotation of the plane of polarization of the reflected light caused by the Faraday effect.
FIG. 1 of the accompanying drawings shows the construction of a magnetic head using the transfer film reproducing method according to the prior art. In FIG. 1, reference numeral 1 designates a magnetic recording medium, reference numeral 2 denotes a reflecting film, reference numeral 3 designates a magnetic transfer film, reference numeral 4 denotes a substrate, reference numeral 5 designates a laser light, reference numeral 6 denotes a laser, reference numeral 7 designates a collimator lens, reference numeral 8 denotes a beam splitter, reference numeral 9 designates an analyzer, reference numeral 10 denotes a condensing lens, and reference numeral 11 designates a photodetector. The magnetic transfer film 3 comprising a magnetic garnet film or the like is generally formed on the substrate 4 of GGG or the like by the LPE growing method, and the light reflecting film 2 of Al or the like is provided on top of the magnetic transfer film, and the reflecting film 2 is brought into intimate contact with the magnetic recording medium 1 to thereby transfer a signal magnetized section as the magnetized section of the magnetic transfer film 3. The laser light 5 emitted from the laser 6 is condensed on the magnetic transfer film 3 through the collimator lens 7, the beam splitter 8 and the condensing lens 10, and is subjected to the Faraday rotation corresponding to the signal magnetized section of the magnetic transfer film 3 and is reflected thereby. The reflected light which has detected the signal returns to the original optical path, has its direction of travel changed by the beam splitter 8, is received by the photodetector 11 through the analyzer 9 and the condensing lens 10 and reproduces information.
By thus detecting the signal through the magnetic transfer film, it is possible to eliminate various problems which may arise when reading is effected with the laser light being directly applied to the recording medium, and there is also an advantage that such a method is better in S/N ratio than the signal detecting method by the Kerr rotation used in a magneto-optical disc. However, in the above-described conventional magnetic transfer system, the use of the optical system as shown in FIG. 1 limits the compactness of the apparatus and, to realize a high transfer bit rate, it is necessary to use a plurality of lasers or to divide the laser light into plural lights by a grating or the like and to apply the plural laser lights to plural tracks at the same time. Also, in this case, a photodetector is necessary for each individual laser light beam, and to construct a multitrack reproducing head having ten tracks, ten laser beams and ten photodetectors are necessary, and this leads to a disadvantage that the construction becomes complicated.